1. Field of the Invention
The present invention relates to a controller for controlling an irradiation direction of a vehicle lamp, and in particular to an irradiation direction controller and a leveling angle setting method, for vertically controlling the irradiation direction of a headlamp in accordance with the tilt angle of the front section of the vehicle in a vertical direction with respect to a road surface.
2. Related Art
When a cargo loading state of a vehicle or number of passengers are changed, a deflection quantity of a spring of a suspension device supporting a vehicle body may change, and an elevation angle formed by a front of the vehicle body with respect to a road surface, that is, a vertical angle of the vehicle in a longitudinal direction with respect to the road surface (hereinafter referred to as a pitch angle) may change. An irradiation angle (optical axis) of a headlamp mounted on a front of the vehicle also may change in the vertical direction following the pitch angle. When the irradiation direction is set upward, another vehicle such as an oncoming vehicle is dazzled. When the irradiation direction is set downward, front irradiation of the vehicle is insufficient. Neither case is preferable in terms of traffic safety. In order to keep constant the irradiation direction of the headlamp irrespective of the change in the pitch angle, there is an auto-leveling device. The auto-leveling device is provided with pitch angle detecting means for detecting the pitch angle of a vehicle, control means for outputting a control signal for adjusting the irradiation direction of the headlamp in vertical direction in accordance with the detected pitch angle, and an actuator for adjusting the angle of the headlamp with respect to the vehicle body based on the control signal.
The auto-leveling device is provided with, as means for detecting the pitch angle of the vehicle body, a vehicle height sensor for detecting the height of the vehicle with respect to the load surface. As a vehicle height sensor, for example, a measuring sensor for measuring the clearance in vertical direction between an axle and the vehicle body is used. A front wheel section and a rear wheel section each is equipped with a vehicle height sensor in order to calculate a pitch angle based on the vehicle height detected at each wheel section. In another option, a vehicle height sensor is provided on one of the front wheel section and rear wheel section in order to calculate a pitch angle based on the detected vehicle height.
During a mounting of the vehicle height sensor on the vehicle body, some mounting error may be occurred. Therefore, in general, an initialization is carried out so as to reset the mounting error to zero. This process is called as a vehicle height value initialization. As a vehicle height value initialization technique is proposed, for example, in JP-A-2003-40029. In the vehicle height value initialization technique of JP-A-2003-040029, a difference between an actual vehicle height and a design vehicle height is recorded as a correction value. The actual vehicle height is a value actually measured by the vehicle height sensor in a reference state where the vehicle body is horizontally even. The design vehicle height is a value calculated from a design of the vehicle. The vehicle height is corrected using the correction value in order to obtain a vehicle height that does not include the mounting error.
FIG. 5 is a flowchart explaining an exemplary general operation of vehicle height value initialization. When a vehicle height value mode switch is turned on (S201), it is determined whether the vehicle height value initialization conditions are satisfied (S202). The vehicle height value initialization conditions include whether the number of passengers is a predetermined value, whether the gas tank is full, and whether the tire air pressure is a predetermined value. When these conditions are satisfied, it is determined that the vehicle is in the reference state and the control means reads the actual vehicle height by the vehicle height sensor (S203). The actual vehicle height value is compared with the preset design vehicle height value. For example, the difference between the two is obtained (S204). The difference is recorded as an initialized value onto recording means (S205). In the subsequent auto-leveling control, the control means corrects a vehicle height value sequentially read from the vehicle height sensor by using the initialized value each time the vehicle height value is read. The control means then replaces the read vehicle height value with the corrected vehicle height value to calculate a pitch angle and a leveling angle. This process allows appropriate auto-leveling control.
By the way, during manufacturing/assembling the vehicle, an inspection process for inspecting whether the auto-leveling device of the headlamp operates normally, and an aiming adjustment process for setting an initial irradiation direction of a headlamp is carried out. The aiming adjustment process adjusts the mechanism of a headlamp so that the irradiation of a headlamp may be oriented in a proper direction when the headlamp is under auto-leveling operation by a controller.
In this way, the aiming adjustment is carried out while the auto-leveling operation is finished by control means. The auto-leveling operation must be normally and correctly finished at the time of aiming adjustment. A mounting error in a vehicle height value obtained from a vehicle height sensor prevents precise auto-leveling. Thus, the vehicle height value initialization must be done before the auto-leveling operation, and then the aiming adjustment must be made.
FIG. 6 is a flowchart explaining the main processes of related art aiming adjustment. First, a vehicle height value is read from a vehicle height sensor (S301). The vehicle height value initialization is performed on the read vehicle height value (S302), and a pitch angle is calculated based on the initialized value obtained by the initialization and a detected vehicle height value (S303). Next, a leveling angle is calculated so as to obtain a preset leveling angle (an angle in vertical direction formed by the irradiation direction of a headlamp with respect to the level direction when the pitch angle of the car body of a vehicle is “0”) in correspondence with the calculated pitch angle (S304), and the actuator of an auto-leveling device is driven based on the calculated leveling angle (S305). After that, the aiming adjustment is carried out so as to set the irradiation direction of the headlamp to a predetermined direction (S306). Thus, assuming that the vehicle height value initialization in step S302 is skipped, the pitch angle calculated based on the read vehicle height contains an error. The leveling angle set in correspondence with the pitch angle also contains an error. The aiming adjustment of a headlamp set to an error-containing leveling angle results in inappropriate aiming adjustment.
In a vehicle assembly plant, when a layout of assembly lines are planed, it may be better that the aiming adjustment is carried out prior to the vehicle height value initialization, for an effective layout. However, in the above related-art, the vehicle height value initialization must be carried out prior to the aiming adjustment process. The related-art approach cannot respond to a request for such a flexible assembly process design.